HVAC systems are commonly used to control various environmental conditions within building structures including, for example, temperature, humidity, ventilation, etc. In doing so, a fan or the like is often used to force air through the HVAC system and provide conditioned air to the inside space of the building structure. When doing so, the air is circulated within the structure. Air circulation can help increase the comfort inside the building structure by, for example, equalizing the temperature, humidity and other environmental conditions within the structure.
Some HVAC systems have one or more circulation modes. For example, some HVAC systems include a fan “on” mode, where the fan is “on” continuously, regardless of whether the HVAC system is called to condition the air in the building structure. A “circulate” fan mode is also sometimes provided, which typically runs the fan for a fixed period of time during each hour, such as 20 minutes each hour. These and other circulation modes may help circulate the air within a building structure.
In some HVAC systems, fresh air ventilation is also provided. Fresh air ventilation has become increasingly popular, especially because new building structures have become more energy efficient and consequently more air tight. Fresh air ventilation is typically used to replace stale air inside the building structure with fresh outside air. Fresh air ventilation often uses the fan of the HVAC system, and thus also provides air circulation within the building structure. Heat exchangers are sometimes used to exchange heat between the outgoing stale air and the incoming fresh outside air to help reduce the energy costs associated with heating or cooling building structure.
While circulation and/or ventilation are often desirable, over-circulation and/or over-ventilation can result in increased energy costs and excessive equipment wear. What would be desirable, therefore, are adaptive circulation and/or ventilation control methods and systems that provide desired circulation and/or ventilation levels, while minimizing energy costs and equipment wear.